Genetic info on Sumatra four spurs.

I know Sumatra breed tends to grow 4 spurs but not always. Wanted to know what anyone knows about the gene that makes it possible and what the likely hood of offspring to carry this trait. More interested in how the trait would carry over if you need a cock with four spurs who kept having cocks who almost always have four spurs then bred a hen of its offspring to another breed. What would the likely be that the mix would develop four spurs. Or would it be more likely to breed the pure Sumatra cock to another breed hen to get the four spurs trait and the need to back breed to further the four spurs gene. Genetics are fun and just thinking.

I know Sumatra breed tends to grow 4 spurs but not always. Wanted to know what anyone knows about the gene that makes it possible and what the likely hood of offspring to carry this trait. More interested in how the trait would carry over if you need a cock with four spurs who kept having cocks who almost always have four spurs then bred a hen of its offspring to another breed. What would the likely be that the mix would develop four spurs. Or would it be more likely to breed the pure Sumatra cock to another breed hen to get the four spurs trait and the need to back breed to further the four spurs gene. Genetics are fun and just thinking.

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In sumatra, there is an incompletely dominant gene that expresses the multiple spur characteristic (3 to 5 spurs per shank). There are also modifiers that can effect the expression of the multiple ( two per shank) spur trait.

Birds that carry one multiple spur gene and a recessive normal spur gene usually have two spurs on each shank.

To produce males with only two spurs on each shank, you would cross a single spurred male with a hen that has or had multiple spurred (3 to 5) male siblings. This is not always the case because some birds carry a modifier or modifiers that cause the male fowl to only have one spur per shank when the gene should express two spurs per shank.

#1 single spur male (no multiple spurs in lineage) x Hen (four spurs per shank carrier)= F1 males with two spurs per shank (unmodified) or males with one spur per shank (modified), hens will be carriers

The above cross (#1) should not produce males with 4 spurs per shank. If you want to maintain the four spurs per shank trait always cross close relatives. Outcrossing to a single spur per shank breed will normally produce two spurs per shank carriers, males will have two spurs per shank.

I know very little about the modifier or modifiers.

F1 male (two spurs per shank) x four spurs per shank carrier female = F1BC1 offspring - some four spurs per shank males and some two spurs per shank males, do not use F1BC1 females for breeding

F1 male x F1 female = F2 mixed bag of males some four spurs per shank, some two spurs per shank, some one spur per shank- can not use F2 females for breeding